1. Field of the Invention
The present invention relates in general to techniques for monitoring and controlling an operation of an injection molding machine for producing a disc substrate, to improve the consistency in the quality of the produced disc substrate. More particularly, the present invention is concerned with an apparatus and a method of monitoring such an injection molding machine, which include a device for or step of displaying operation data of the machine, and a control apparatus for controlling the machine by using such a monitoring apparatus.
2. Discussion of the Related Art
Generally, a disc substrate used for molding an optical or magneto-optical disc is advantageously produced by injection molding using a resin material. Such a disc substrate is required to have a high degree of dimensional accuracy and excellent physical properties. To meet this requirement, an operation of an injection molding machine adapted to mold the disc substrate is required to be controlled with high accuracy and stability. To control the operation of the injection molding machine, it is considered to monitor its operating condition, by detecting an injection speed, an injection pressure, an operating position of an injection screw and other operating parameters, with suitable sensors or detectors. Operation data of the machine represented by the output signals of these sensors are stored in a memory, and are displayed on a suitable display device such as an oscilloscope.
JP-A-7-205245 (publication of an unexamined Japanese patent application) discloses a data analyzing apparatus including a microcomputer which is adapted to: process the output signals of various sensors provided on an injection molding machine; store operation data of the machine based on the output signals for each cycle of injection molding to produce a disc substrate; analyze the stored operation data; and display the stored operation data on a display device, together with numerical values obtained as a result of the analysis.
Such a known data analyzing apparatus is adapted to simply display the operation data, which are continuously varying during an injection molding operation of the machine. Therefore, the user or operator of the machine who observes the display device has difficulty to accurately estimate or recognize an influence of the present operating condition of the machine on the quality of the injection molded product. The machine operator is required to have long experience and intensive and extensive professional knowledge in order to monitor the operating condition of the machine based on the operation data provided on the display device. Thus, the known data analyzing apparatus does not assure a high degree of consistency in the quality of the product.
The above-identified publication also discloses a technique for displaying maximum and minimum values, rise and fall times and other numerical values of various operating parameters of the machine, which have been obtained by analyzing the stored operation data. However, those numerical values displayed are also operating parameter values which are continuously varying from time to time and which do not enable the machine operator or user to accurately monitor the operating condition of the machine.
Further, the known data analyzing or monitoring apparatus is arranged to store and analyze operation data obtained by the sensors and analyze the obtained operation data for each injection molding cycle or shot, and display a result of the analysis on the display device in the next injection molding cycle or cycles. Actually, however, this arrangement does not permit a prompt manipulation to adjust the operating condition of the machine based on the displayed data, during a series of injection molding cycles. Thus, the known apparatus suffers from a delayed feedback of the operation data to adequately control the injection molding operation.